LOL, Mirai Nikki. That was bloody brilliant. I honestly think that Uryu is my favorite character from the series rather than that pinked hair yandere. She also got her own original anime only episode from the series that wasn't from the manga.

I mean that is true for that base, however, like I stated somewhere before, there are a lot of those teenagers from years back who enjoyed that but they ar enow twenty somethings that still love anime. I am one of those myself and know a ton more. Im just saying i think it would be wise to cater to these twenty some year olds since they are the teenagers form the past years who would still tap into the anime/manga market if they could relate more to the material. I mean it would not be that hard honestly, you could take general plot ideas from the teenage shows/mangas and apply them to older crowds with them dating, getting married, getting divorced, having kids, going it alone, i mean there are tons more situations you can apply the ideas to than with the teenage crowd alone. Plus, i am sure many teenagers who are in their 17-19's would pick these up in a heart beat as they could start to relate more. I mean are there any people out there who are reading this and are in college now or 20-30's and wouldn't want something geared toward this?

But remember, the target audience is Japanese, which is a country that is in the midst of a population crisis, with the population expected to decrease by one-third by 2060, largely due to a decrease in the number of young people who are getting married and having children. In a report on the possible reasons for this decline, a student recently quoted the following:

a study by a group in Japan called the Japan Family Planning Associationrevealed that the number of males age 16 to 19 that were indifferent or averse to sex rose by 19% to a total of 36% between 2008 and 2010

Regardless of the direction of causality (does life imitate art or art imitate life?) this shows a strong trend in the young male demographic to be at least indifferent to the concept of marriage. (If they aren't interested in sex, it stands to reason they are even less interested in marriage.) This seems rather strange to those of us in the US, particularly those of us that were once 16-19 year-old boys. I don't recall those years perfectly, but I do recall that I was intensely interested in sex at the time, regardless of the general disinterest the girls I knew had in the topic, at least when the topic included me personally.

In any case, this type of cultural shift makes it even less likely that people will be making manga and anime that feature marriage as a prominent part of the story-line. I expect that it will continue to be used mostly as the butt of jokes about the thirty-year old single teachers and their inability to attract husbands and not as the main story of the protagonists, or even the main long-term goal of the protagonists when it comes to their romantic entanglements.

I haven't seen an anime that has a main focus on marriage, but I have seen marriage being a component of the anime.

For examples, in BTOOOM!!!, there is a marriage breakdown between the protagonist's parents leading to events in the anime.
In Kokoro connect, also touched on some domestic violence issues for one of the character, Iori I think, I can't remember exactly.

And in Magi: The Labyrinth of Magic, one of the princesses was forced to marry for political reasons, although the marriage did not proceed.

So I think marriage is a component, but it has never been the main focus of an anime.

Natsuyuki Rendezvous is the most recent anime I can think of where a marriage is the main focus but it is because...

Spoiler Alert! Click to show or hide

Her husband has died and is haunting her while the former customer/new assistant is trying to date her.

Otherwise there are few parents to see in most shows. One or both are often dead or aren't around for some reason. These dead parents are often an important part of the story in many.

Spoiler Alert! Click to show or hide

Tari Tari, Nazo no Kanojo X, Say "I Love You"

. Deadbeat fathers, drunken fathers, drunken mothers, player fathers, player mothers... I would say normal familes are not that common in anime!

This is fairly new however. I can remember a time when a wedding episode was an exciting and highly anticipated event in anime. I don't think it was that uncommon in the '70s and '80s but perhaps not that common for the main protagonist. He was often the best man or wing man but usually more of a loner/player than a marrying type IIRC.

Pretty sure it's all to do with the target demographics, which has been said above. ^

Looking through my MAL the stories that involve (or at least contain) relevant marriages are shows like Bakuman, Fate/Zero, Legend of the Galactic Heroes, and Texhnolyze; with a couple others that at least deal with adult romantic relationships (like Cowboy Bebop, Durarara!!, and Kara no Kyoukai).

All of which are definite outliers in at least some sense in terms of the kind of audience they're targeting.

I mean that is true for that base, however, like I stated somewhere before, there are a lot of those teenagers from years back who enjoyed that but they ar enow twenty somethings that still love anime.

People of all ages in japan read manga to some degree or another, however anime is seen primarily as an activity for children. Upon becoming an adult it is the norm to leave anime entirely behind, with women iirc leaving it behind earlier than men. So while many adults may fondly remember watching anime as a kid, to continue to watch it is considered abnormal. Its why most anime is Shounen or Shoujo, with the somewhat less common Seinen which mainly survives due to teen males and adult otaku. There's plenty of manga out there that deals with marriage and other adult life stuff, but you're going to find a good chunk of it in Josei and the occasional Seinen work which are much less likely to be adapted into an anime.

Try to write or suggest something criticizing about how Japanese animation views and/or treats the female gender in anime and see if it gets posted without some form of electronic censorship. There was a series last season where I tried to post some feminist viewpoints in the comment section near the end of the series. I tried three times. I re-worded my declarative statements 3 different ways to arrive at the same conclusion, all to no avail. The CR software picked out certain key words and my comment(s) would not post. There were no expletives, epithets, curse words, or other inflammatory rhetoric in the sentence structure. Ultimately, I wrote something simplistic and poignant....that got approval by the software and was "posted" with no delay.